Marriage
Queen Louise wanted her eldest son to marry as well as had her two daughters, Alexandra and Dagmar. Queen Victoria of the United Kingdom had two yet unmarried daughters, Princess Helena and Princess Louise, and Queen Louise planned to have Frederick marry one of them. During his stay in England, Crown Prince Frederik actually took an interest in Princess Helena, and although his feelings were reciprocated, the connection did not materialize, as Queen Victoria opposed it. Victoria did not want her daughters to marry heirs to foreign thrones, as this would force them to live abroad, instead preferring German princes who could establish homes in England. In addition, Victoria had always been pro-German and another Danish alliance (Frederick's sister, Alexandra, had married Victoria's eldest son Albert Edward, Prince of Wales), would not have been in line with her German interests.
After this failed marriage attempt, attention turned instead to Princess Louise of Sweden, the only daughter of King Charles XV of Sweden. Princess Louise belonged to the Bernadotte dynasty, which had ruled in Sweden since 1818, when the founder, Jean-Baptiste Bernadotte, one of Napoleon Bonaparte's generals, was elected crown prince of Sweden in 1810 and later succeeded the throne as King Charles XIV John in 1818. He married Désirée Clary, who had once been engaged to the French Emperor. Charles XIV's son, Oscar I, had married Josephine of Leuchtenberg, the granddaughter of Napoleon's first wife, the Empress Josephine. King Oscar I and Queen Josephine were Princess Louise's paternal grandparents.
The marriage was suggested as a way of creating friendship between Denmark and Sweden. Relations between the two countries had been tense after Sweden had not assisted Denmark during the war with Prussia in 1864. Frederick and Louise had met for the first time in 1862, but in 1868, Frederick was invited to Sweden to get to know Louise, and their meeting was described as a success. In July that same year, Crown Prince Frederick—then 25 years old—became engaged to the 17-year-old Princess Louise. A year later, they were married in the chapel at the Royal Palace in Stockholm on 28 July 1869. Louise was the first Swedish princess to be married into the Danish royal house since the Middle Ages, and the marriage was welcomed in all three Scandinavian countries as a symbol of the new Scandinavism.
On 10 August 1869, the newlyweds made their entrance into Copenhagen, where they received a warm welcome. As their residence, the couple was awarded Frederik VIII's Palace, an 18th-century palace which forms part of the Amalienborg Palace complex in central Copenhagen. As their country residence they received Charlottenlund Palace, located on the shores of the Øresund Strait 10 kilometers north of Copenhagen. Here they had a refuge far away from court life at Amalienborg and here several of their children were born. Frederick and Louise had four sons and four daughters born between 1870 and 1890: Prince Christian, Prince Carl, Princess Louise, Prince Harald, Princess Ingeborg, Princess Thyra, Prince Gustav and Princess Dagmar. Their eldest sons, Christian and Carl, would become kings of Denmark and Norway respectively. Due to the many children, Charlottenlund Palace was rebuilt to accommodate the large family, and in 1880–81, the palace was expanded with a dome and two side wings.